1. Technical Field
This disclosure relates to a technology for notifying information about an event occurring in one device to other devices.
2. Description of the Related Art
Network image processing devices, such as printers, are known in the art that can receive operation instructions from other devices (users) via a network, such as the Internet or Intranet. When an event occurs in such an image processing device, it notifies information about the event to all of its users. As a result, the users can grasp the content of the event and execute appropriate operations. Such events generally relate to the hardware or software conditions in the image processing device.
When notifying information about an event to the users, the information is simultaneously sent to all the users. Because the information is simultaneously sent to all the users, traffic on the network temporarily suddenly increases, resulting in the decrease of the response speed. Japanese Patent Application Laid-open No. 2001-282471 teaches to provide a delay, if the number of the users is large, in sending the information to some of the users. With this arrangement, a rapid increase in the traffic is prevented, and a reduction in the response speed is avoided.
In the technique disclosed in Japanese Patent Application Laid-open No. 2001-282471 there exists a problem that the occurrence of the event cannot be notified to all users.
For example, consider that the image processing device monitors events at 2-second intervals, and a first even occurs at a certain time and a second event occurs 2 seconds after the first even. In this case, there can be some users who do not receive the information about the first event although the second event has already occurred. In other words, there arises inconsistency that some users receive the information about the first event after the occurrence of the second event. Consequently, the user can get confused. That is, the event occurrence information can be correctly notified to all users in the case of an example shown in FIG. 34A. The event occurrence information cannot be correctly notified in the case of an example shown in FIG. 34B, and a user who cannot receive the notification within 2 seconds will receive a notification of old information.
As another example, because of a long validity period of requesting an event notification to plural devices, the number of users who request the notification becomes large, and this has a risk of generating a delay in the notification process.